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BSC 215 Exam 1 Study Guide

by: Regan Dougherty

BSC 215 Exam 1 Study Guide BSC 215

Marketplace > University of Alabama - Tuscaloosa > Biology > BSC 215 > BSC 215 Exam 1 Study Guide
Regan Dougherty
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The topic for this exam is Cellular Form and Function. This study guide contains lecture notes and information from the textbook. Exam date: 2/17/16
Human Anatomy & Physiology 1
Jason Pienaar
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This 22 page Study Guide was uploaded by Regan Dougherty on Friday February 12, 2016. The Study Guide belongs to BSC 215 at University of Alabama - Tuscaloosa taught by Jason Pienaar in Spring 2016. Since its upload, it has received 71 views. For similar materials see Human Anatomy & Physiology 1 in Biology at University of Alabama - Tuscaloosa.


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Date Created: 02/12/16
Exam Date: 02/17/16 BSC 215 Exam 1 Study Guide Cellular Form and Function - Seven Characteristics of Life: Homeostasis - maintenance of the body’s internal environment • - Regulated vs. Non-regulated variables • Organization • Metabolism - all chemical processes that occur in a living organism • Growth • Adaptation • Response to stimuli • Reproduction • **In addition, all living things have cell membranes and hereditary material (double stranded DNA). - Feedback Loop - a homeostatic control mechanism in which a change in a regulated variable causes effects that feed back and affect that same variable • How it works: the receptor (or sensor) senses a stimulus (caused by a regulated variable being outside of its normal range). The receptor sends this information to a control center. The control center sends signals to effectors, which cause a response. • Negative Feedback Loop - the response in which the change in a regulated variable in one direction results in actions that cause changes in the variable in the opposite direction - Ex. body temperature • Positive Feedback Loop - a homeostatic control mechanism in which a change in a regulated variable causes effects that feed back and affect that same variable - Positive feedback loops are often found within a negative feedback loop. - Ex. formation of a blood clot, childbirth 1 Exam Date: 02/17/16 - Structure and Function are Related. • Ex. blood vessels, bones, bladder, lungs (All of their forms follow their function.) - Gradient - a condition in which more of something exists in one area than another, and the two areas are connected • Temperature gradient • Concentration gradient • Pressure gradient - Cell Communication • Two necessary components: ability to generate a signal nd ability to receive that signal • Chemical Signaling - Endocrine - long distance signaling (usually involves the bloodstream) - Paracrine - communication between cells within a tissue (short distance signaling) - Autocrine - cell signals to itself - Juxtacrine - the two communicating cells are attached • Electrical Signaling - involves the flow of ions across membranes - Matter - anything that occupies space and has mass • States of Matter - Solid - defined shape and volume - Liquid - undefined shape, defined volume - Gas - undefined shape and volume - Atom - the smallest unit of matter that still retains its original properties • Protons - charge: +, weight: 1 AMU • Neutrons - charge: none, weight: 1 AMU • Electrons - charge: -, weight: none • Atomic number - number of protons 2 Exam Date: 02/17/16 • Atomic mass - number of protons + number of neutrons - Element - simplest form of matter to have unique chemical properties • 4 most abundant elements in living things: carbon, hydrogen, oxygen, nitrogen • Most prevalent bond in the body: covalent bond - Isotopes - atoms of the same element that differ only in the number of neutrons (and, consequently, mass) • Radioisotopes - unstable isotopes that decay over time - Radioactive decay - emission of particles from the nucleus of an atom • Alpha particle (ɑ) - 2 protons and 2 neutrons - results in change in atomic number and atomic mass - low penetrance • Beta particle (β) - electron - low penetrance • Gamma ray (????) - high energy photon - Two ways to combine matter: • Mixtures - different atoms combined retain their unique chemical properties and can be physically separated - Suspensions - solids suspended in a liquid; particles settle out when undisturbed • Ex. blood - Colloids - solids suspended in a liquid; particles are smaller than those in a suspension and do not settle out • Ex. milk - Solutions - one thing is dissolved in another Ex. glucose and water • • Solute - what is dissolved • Solvent - what the solute is dissolved in 3 Exam Date: 02/17/16 • Chemical bonds - an energy relationship between atoms or ions caused by the sharing or transfer of valence electrons; the resulting molecules have different properties than the reactants - Ionic bonds - transfer of electrons between atoms resulting in an attraction between the atoms (because of their opposite charges) • Cation - positive charge • Anion - negative charge - Covalent bonds - formed when 2 atoms share electrons • Non-polar covalent bonds - equal sharing of electrons • Polar covalent bonds - unequal sharing of electrons - The electrons will spend more time near the bigger nucleus (because it is more positive). • Covalent bonds get stronger and stronger the more electrons that are shared (Double covalent bonds are stronger than single; triple covalent bonds are stronger then double.). - Hydrogen bonds - attractions between polar molecules (The positive side of one atom attracts the negative side of another.) • Gives water the following properties: surface tension, solvency, cohesion, adhesion, chemical reactivity, thermal stability - Van der Waals forces - brief attractions between temporarily polar molecules (depending on electron activity/location) - The valence shell determines reactivity. • Octet rule - An atom is most stable when its valence shell contains 8 electrons - Duet rule - for smaller atoms, they are most stable when they have 2 valence electrons - Chemical reaction - chemical bonds are broken, formed, or rearranged or electrons are transferred/shared between atoms • Types of Chemical Reactions - Decomposition/Catabolic - products are smaller molecules than the reactants 4 Exam Date: 02/17/16 • AB —> A + B - Synthesis/Anabolic - product is bigger molecule than the reactants • A + B —> AB - Exchange - “trading partners” • AB + CD —> AC + BD - All 3 types are reversible. - Three Forms of Energy (the capacity to do work) • Chemical energy - potential energy stored in bonds • Electrical energy - flow of ions (across cell membrane) - generally used for communication between cells • Mechanical energy - energy transferred from one object to another through contact • Endergonic reaction - products have a higher energy than the reactants - consumes energy • Exergonic reaction - reactants have a higher energy than the products - releases energy - Factors that Influence Reaction Rate • temperature • concentration • reactant properties (ex. solid / liquid / gas) • catalysts - Enzymes - lower activation energy required to make or break covalent bonds • Activation energy - energy required for a chemical reaction to happen // for example, the energy required to help molecules overcome the repulsive forces of electrons • Enzymes are highly specific. They have specific shapes that fit specific molecules. • Enzymes are reusable; they come out of a reaction is their original form. 5 Exam Date: 02/17/16 • Hydrolysis - breaking a bond by the addition of a water molecule - Properties of Water • High heat capacity - absorbs and releases heat without significantly changing temperature itself • High heat of vaporization - requires a lot of heat to transition from a liquid to a gas • Highly reactive - easily interacts with molecules in chemical reactions • Adhesive & Cohesive - acts as a lubricant between two adjacent surfaces - Adhesion - water molecules stick to other surfaces - Cohesion - water molecules stick to each other • (Relatively) High density - cushions and protects the body’s structures Polar solvent - polar molecules completely dissociate (into separate ions) in the • presence of water - This property is due to the polarity of water (H is slightly positive and O is slightly negative). - Acids and Bases • Acid - proton donor (release hydrogen ions (H+) into solution) - [H+] in solution determines the acidity of the solution. • Base - proton acceptor (takes H+ out of solution) - release hydroxyl ions (OH-) into solution - [OH-] in solution determines alkalinity • All acids and bases are electrolytes. - They ionize and dissociate in water. - The pH Scale (ranges from 1-14; 7 is neutral) • pH measures the concentration of H+ in solution. • pH = negative logarithm (base 10) of [H+] in solution • higher [H+] —> lower pH (more acidic) • lower [H+] —> higher pH (more alkaline/basic) 6 Exam Date: 02/17/16 • [H+] is inversely related to pH - Buffer - molecule that prevents rapid shifts in pH • Buffers include weak acids and bases that maintain equilibrium. - release H+ into solution as pH rises ([H+] decreases) - bind H+ out of solution when pH falls ([H+] increases) - Ex. Carbonic acid • can act as an acid or base depending on the pH of the solution - Organic compounds usually include a carbon backbone (carbons linked together by covalent bonds). • Organic compounds differ by their functional groups. - 5 functional groups to know: • Hydroxyl (-OH) - commonly found in carbohydrates • Methyl (-CH )3- commonly found in lipids and amino acids • Carboxyl (-COOH) - commonly found in lipids and amino acids • Phosphate (-H P2 ) -4commonly found in nucleic acids • Amino (-NH )2- commonly found in amino acids - Monomers and Polymers • Polymer - macromolecule made up of repeating identical or similar submits - These subunits are called monomers. • Dehydration synthesis - anabolic reaction (molecules are built) in which two monomers are linked by a covalent bond and a water molecule is released - Water is formed from the H from one molecule and OH from another molecule. • Hydrolysis - catabolic reaction (molecules are broken down) in which the covalent bond linking the monomers is broken by the addition of water molecule atoms - Carbohydrates • Contain carbon, hydrogen, and oxygen in a ratio of 1C:2H:1O or CH O. 2 • Monomers: monosaccharides // Polymers: polysaccharides 7 Exam Date: 02/17/16 • Carbohydrates are hydrophilic (because they contain several OH groups). • Ex. glycogen (stored/synthesized in liver, muscles, brain, uterus, vagina) - Lipids • Contain carbon, hydrogen, and oxygen in a different ratio than carbohydrates. - Monomers: ~(1C:2H)n:2O • There are usually 2 hydrogens for every carbon and 2 oxygens in total. - Ex. C 15CO31 (fatty acid) - Polymers: triglyceride is most common • Triglyceride: 3 fatty acids + glycerol - fatty acid storage in fat/adipose tissues; building block of phospholipids • Steroids have ring structures. - form the basis for cholesterol and hormones (ex. testosterone and estrogen) Lipids are typically hydrophobic. • • Fatty acids - serve as energy molecules and building blocks for polymers - Saturated - no double bonds; solid at room temperature - Monounsaturated - one double bond; liquid at room temperature (lower melting point) - Polyunsaturated - multiple double bonds; liquid at room temperature (even lower melting point) • Phospholipids - make up cell membrane; glycerol + 2 fatty acids + phosphate group - Proteins • Proteins are recognizable by their complex shapes. • Contain carbon, hydrogen, oxygen, and nitrogen. • Monomers: amino acids (There are 20 different amino acids.) - Components of amino acids: • central carbon 8 Exam Date: 02/17/16 • amino group • carboxyl group • R group (variable) • Polymers: polypeptides/proteins • Structure - Primary - amino acid sequence - Secondary - folds in an amino acid chain (ex. alpha helix, beta pleated sheet) - Tertiary - final 3D structure, interactions among R groups - Quaternary - multiple polypeptide chains • Collagen (fibrous protein) • Enzymes (globular proteins) - Nucleic Acids • Contain carbon, hydrogen, oxygen, nitrogen, and phosphate. • Monomers: nucleotides • Polymers: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) - DNA nucleotides have one less oxygen than RNA nucleotides. • DNA serves as hereditary material. • ATPis a source of energy. Cell Theory: 1. All living organisms are composed of cells. 2. The cell is the most basic unit of life. 3. All cells come from pre-existing cells. - Morphology - shape and size • Cells exist in a huge variety of shapes and sizes. • Most human cells are 10-15 micrometers in diameter. • Cell size is limited because of their surface to volume ratio. 9 Exam Date: 02/17/16 - surface divided by volume - A larger surface to volume ratio is more likely. - If the surface to volume ratio is not big enough, the surface may not be able to support the volume of the cell. - All cells are made of 3 basic components: • Plasma membrane • Cytoplasm (intracellular space) - Cytosol - liquid part - Organelles are dissolved in the cytosol. • Nucleus - contains double stranded DNA - surrounded by nuclear envelope (double membrane) - Cell Membrane • composed of: - Lipids • Phospholipid - fatty acid tails are hydrophobic (not charged) and the phosphate group is hydrophilic (charged) - amphipathic - containing both hydrophilic and hydrophobic parts - forms a phospholipid bilayer - The fatty acids will be on the inside of the bilayer and the phosphate groups will be on the outside of the bilayer. • Cholesterol - Cholesterol molecules are stiffer molecules than phospholipids, so their job is to stiffen the plasma membrane. - More cholesterol = stiffer membrane • Glycolipids - carbohydrate covalently attached to a lipid • form part of the glycocalyx (sugar coating) 10 Exam Date: 02/17/16 - Proteins • peripheral - associated with either the intracellular or extracellular face of the plasma membrane • integral - spans the width of the plasma membrane • Some amino acids are hydrophilic and come are hydrophobic, so proteins are able to interact with both the hydrophilic and hydrophobic parts of the membrane. • Roles of proteins in the cell membrane: - Receptor - bind specific chemical messengers and transmit the signal to the cytoplasm - Enzyme - catalyze reactions • Enzymes require a surface to work on (keeps the enzyme in place). - Channel - allow hydrophilic molecules and water to pass through the membrane - Gated channel - ligand (chemical), voltage, or mechanically gated channel • The channel is closed until it is opened by some sort of stimulus. - Identity marker - glycoproteins distinguish “self” from “non-self” • Glycoprotein - carbohydrate and protein that are covalently linked - Cell adhesion molecule (CAM) - cell-cell binding and mechanical connections to extracellular matrix (ECM) - Carbohydrates Glycocalyx • • Unique identifier for cells - immune functions (distinguishing “self” from “non-self” - adhesive functions (allows cells to stick to various things) - Passive Transport - movement across a membrane down a concentration gradient (DOES NOT require energy) • Diffusion - movement of solute down a concentration gradient 11 Exam Date: 02/17/16 - high concentration —> low concentration - Why do molecules move like this? kinetic energy of random motion - Diffusion across a membrane • Cell membranes are selectively permeable. - Selectivity is based on: • size charge (Hydrophobic molecules travel through the membrane more easily • than hydrophilic molecules.) • membrane protein specificity - Diffusion: Simple vs. Facilitated Simple diffusion - diffusion across the phospholipid part of the membrane • - small molecules • Facilitated diffusion - diffusion through a protein - Molecules still move down a concentration gradient, so no energy is required. - Carrier-mediated - protein carrier specific for one chemical; protein changes shape to transport the chemical across the membrane - Channel-mediated - protein channel allows lipid-insoluble small molecules to pass through • Factors Affecting Membrane Diffusion Rate - Temperature - higher temperature means that the particles are moving faster, so they will flow more quickly across the membrane - Molecular mass - larger molecules will diffuse more slowly - Concentration gradient - the bigger the difference in concentration, the faster the molecules will diffuse - Membrane surface area - the larger the membrane surface area, the more space there is for solutes to move into/out of the cell - Membrane permeability - the more permeable the membrane, the faster the rate of diffusion 12 Exam Date: 02/17/16 - Osmosis - diffusion of solvent (water) molecules down a concentration gradient • passive transport • Dissolved solutes determine the water concentrations. - Tonicity - a comparison between the osmotic pressure of 2 solutions • Hypertonic - solution with a higher concentration of solute • Hypotonic - solution with a lower concentration of solute Isotonic - solutions with equal solute concentrations • • **These are relative terms. • Tonicity is important for red blood cells. - RBCs want to be in an isotonic solution. - If the RBC is in a hypotonic solution, it will swell (water will flow into the cell) and the cell will eventually burst. - If the RBC is in a hypertonic solution, it will shrink (water will flow out of the cell). - Aquaporins - channel proteins that allow water to diffuse through • Some water can diffuse across the plasma membrane because it is a small molecule, but osmosis across a membrane is slightly hindered because water molecules are charged. • The cell controls osmotic rate by varying the number of aquaporins in the membrane. - Active Transport - transport against a concentration gradient; requires energy • Primary Active Transport - membrane protein uses ATP energy directly to pump against a concentration gradient - ATP has high energy bonds. When you break bonds of ATP, energy is transferred to the protein. The protein changes its shape and transports a substance across the membrane. ATPase - enzyme that breaks down ATP to get energy • • Secondary Active Transport - a primary active transport pump establishes a concentration gradient; the potential energy of this gradient is then used to fuel the transport of a second molecule against its concentration gradient 13 Exam Date: 02/17/16 • Vesicular Transport - membrane vesicles bud off of the membrane to transport a large number of molecules • 3 Classes of Protein Pumps - Uniport - transports one thing at a time - Symport - transports 2 or more things in the same direction - Antiport - transports 2 or more things in the opposite direction • Syport and antiport fall under the category of cotransport. - Sodium Potassium Pump - maintains a high Na+ concentration outside the cell; maintains a high K+ concentration inside the cell (ex. of primary active transport) • Some Roles: - nerve cell signaling - skeletal muscle contraction - heart beat - osmotic balance • antiporter-like activity Sequence of Events • - 1. 3 Na+ bind to pump. This stimulates phosphorylation by ATP. - 2. Phosphorylation changes the shape of the pump. This shape change expels the Na+ outside of the cell. - 3. 2 K+ bind on the outside of the cell. - 4. K+ triggers phosphate release (dephosphorylation). This causes the protein to revert to its original shape. - 5. The original shape causes K+ release inside of the cell. - 6. Step 1 begins again (it is a cycle). - Glucose Symporter (ex. of secondary active transport) • The sodium potassium pump creates an ion gradient. The potential energy associated with the sodium gradient is used to transport glucose across its concentration gradient. 14 Exam Date: 02/17/16 - Vesicular Transport (active transport) • Endocytosis - vesicular transport into cell - Forms an endosome (vesicle into which substances are ingested). - Phagocytosis - “cell eating” • ex. white blood cells - Pinocytosis - “cell drinking” - Receptor mediated endocytosis - specific substances are taken into the cell after binding with a receptor on the plasma membrane surface • ex. intake of LDL cholesterol • Exocytosis - vesicular discharge out of cell - Cytoskeleton and Organelles • Mitochondria - power plant of the cell (it makes ATP) - Double membrane • The inner membrane forms cristae (folds). - The function of folds is to increase surface area. • A mitochondrion contains its own genome and its own ribosomes. - Endosymbiotic theory • Ribosomes - protein synthesis; composed of large and small protein subunits - Every living organism has ribosomes because every living organism needs to make proteins. - Locations: • free in cytosol • bound to rough ER or nuclear membranes • Endoplasmic Reticulum - network of cisternae (tubules) continuous with the nuclear membrane - The rough ER is studded with ribosomes. • Folds proteins 15 Exam Date: 02/17/16 • Embeds proteins into phospholipids (creates prefabricated cell membrane sections) - The smooth ER does not have ribosomes. • Calcium ion storage (especially in muscle cells) • Detoxification reactions (especially in the liver) • Lipid synthesis (phospholipids, cholesterol) • Golgi Apparatus - small system of cisternae - smaller and further away from the nucleus than the ER; cisternae are wider than ER - Synthesizes carbohydrates - Adds carbohydrates to proteins received from ER (glycoproteins) • Peroxisomes - produced by rough ER - Oxidize toxic substances (to hydrogen peroxide (H O )2 2 • contains oxygen free radicals (dangerous to cell) - Break down fatty acids - Synthesize some phospholipids (many building blocks are available because of all of the molecules that have been broken down) • Lysosomes - produced by golgi apparatus - contain acid hydrolyses to digest bacteria and worn out cell components • Endomembrane system - a group of organelles consisting of the ER, Golgi apparatus, and lysosomes that together work to process substances imported to and exported from the cell - Nuclear envelope - Rough and smooth ER Rough ER - proteins are folded and modified • 16 Exam Date: 02/17/16 - side function: produce peroxisomes • Smooth ER (see above) • Products from the rough and smooth ER are packaged in transport vesicles and merge with Golgi apparatus. - Golgi apparatus • Lipids and proteins are packaged in transport vesicles and fuse with the plasma membrane. The molecules in the vesicles can either be secreted or become part of the plasma membrane. side function: lysosomes • - Lysosomes and Peroxisomes • Cytoskeleton - a network of protein filaments within a cell that supports the cell, maintains its shape, holds its organelles in place, and functions in cellular motion - perform specialized functions • ex. phagocytosis - 3 types of protein filaments make up animal cell cytoskeletons: • Microfilaments (shown in red in pictures) - made up of a protein called actin - Microfilaments are smaller than microtubules (about 7-9 nm in diameter). - form terminal web (found at the base of microvilli) - extend into microvilli (increase surface area of a cell for quicker transport) • milking - actin filaments shorten microvilli pushing absorbed contents into cell - Common in the outer part of the cell, near the plasma membrane • Intermediate filaments (shown in blue in pictures) - the protein component depends on the type of cell - about 10 nm in diameter (intermediate in diameter - between microfilaments and microtubules) - give cell shape (purely structural role) • Microtubules (green) - made up of protein called tubulin 17 Exam Date: 02/17/16 - about 25 nm in diameter - radiate from centrosomes/centrioles, hold organelles in place - act as “railway tracks” for organelle movement - *movement* - axonemes, mitotic spindles • Cellular Extensions - Microvilli - increase surface area; plasma membrane extensions actin filaments/microfilaments connected to terminal web • • found in intestine, kidneys - Cilia • Primary cilia - sends and receives signals - every human cell has one • Secondary cilia - move things on the surface of cells - respiratory tract, uterine tubes, brain ventricles, testes - motile (move) - beat in waves to propel substances • must beat in a non-viscous (non-sticky) saline (salty) solution - Formation of saline Layer - Cl pumps pump Cl- through membrane (active transport) and Na+ follows by electrical attraction (passive transport) and water follows by osmosis. • In cystic fibrosis, chloride pumps are not embedded in the membrane. This results in no saline solution and no movement of mucus. - Axoneme - made up of 2 central, 9 peripheral microtubules (9+2 structure - 9 surrounding and 2 in the middle) • Cilia and flagella sprout from basal bodies. - Dyenin arms use ATP energy to crawl up adjacent molecules, causes bending and power stroke (movement). - Flagellum - movement (only found in sperm cells in humans) • identical axoneme to secondary cilia (9+2) 18 Exam Date: 02/17/16 - However, flagella are much longer and stiffer. - beat in an undulating motion - Pseudopods - temporary projections of cell membrane; membrane extends into environment (actin filaments) • ex. grabs bacteria from environment and sends to lysosomes - Genetics • Nucleus - cellular control center - Largest organelle (because it contains the largest macromolecule (DNA)) - Contains genes (sequences of DNA that encode for a sequence of RNA that plays a role in protein production). • Determines which proteins a particular cell will make by selectively expressing sets of genes (Different cells produce different proteins.) • Genome - all the DNA contained within a typical cell - Mature RBCs do not have a nucleus.Their primary job is to transport oxygen, so the nucleus just takes up space that could be used for oxygen - Some muscle and liver cells have multiple nuclei because they are so large. • determines which proteins a particular cell will make by selectively expressing sets of genes - Different cells produce different proteins - Nuclear envelope • Double membrane (4 phospholipid layers) - The outer membrane is continuous with the rough ER. • Ribosomes are embedded on the cytoplasmic side of the nuclear membrane (and ER). • The inner membrane is supported by a set of intermediate filaments called the nuclear lamina. • Nuclear pores facilitate active transport of RNA (out), proteins (in), and chemical messengers (both). 19 Exam Date: 02/17/16 - Nucleoplasm - cytoplasm of the nucleus (contains salts, nutrients, nucleotides, and enzymes) • Nucleolus - a specific area in the nucleus where ribosomes are produced - The nucleolus is just a specific area; it is not its own organelle. - Chromatin - a long, thin strand of DNA and its associated proteins • One of the major ways we regulate which genes will be displayed in a cell is whether or not a gene is packaged into chromatin. - If it is highly packaged, it will most likely not be displayed. • Chromatin composition: 30% DNA, 60% histone protein, 10% RNA - DNA is negatively charged, histones are positively charged. • Histones - proteins that aid in the packaging of DNA - A strand of DNA is wrapped twice around each histone protein and the histone proteins condense. - Chromatin condenses on a protein scaffold to form chromosomes. • You only see DNA condensed into chromosomes right before cell division. • Structure of a Chromosome: - 2 identical arms of DNA (sister chromatids) • There are 2 identical arms because the DNA has been replicated. - Chromatids are joined at a centromere. Each chromatid has a kinetochore at the centromere. • • Components of a Nucleotide - Pentose sugar • ribose has an OH on the 2’ carbon • deoxyribose has an H on the 2’ carbon - Phosphate group(s) • attached to 5’ carbon - Nitrogenous base 20 Exam Date: 02/17/16 • attached to 1’ carbon • Adenine (A), Thymine (T) (only in DNA), Uracil (U) (only in RNA), Cytosine (C), Guanine (G) • A guanine in DNA is exactly the same as a guanine in RNA. • Nucleotides come together through dehydration synthesis. - Associated enzyme: DNA/RNA polymerase - Phosphodiester covalent bond - linkage between the 3’ carbon of one sugar and the 5’ carbon of another sugar in DNA and RNA • The sequence of nucleotides determines the sequence of amino acids and, consequently, what type of protein is made. • Hydrogen Bonds - T always hydrogen bonds with A (DNA) • There are always 2 hydrogen bonds. - U always hydrogen bonds with A (RNA) • There are always 2 hydrogen bonds. - C always hydrogen bonds with G • There are always 3 hydrogen bonds. - The width of DNA is always constant. • DNA strands are antiparallel. Transcription - the process by which a specific gene is copied into a complementary • mRNA strand that will be used for protein synthesis - takes place in the nucleus - DNA and RNA polymerase are found in the nucleus. - DNA/RNA molecules grow from 5’ to 3’. • DNA exists as a double helix in cells. This form is extremely stable. • Translation - the process by which RNA dictates the sequence of amino acids to create a protein 21 Exam Date: 02/17/16 - Types of RNA • RNA is usually single stranded; sometimes it folds back on itself to form partial double strands (complimentary base pairing). • mRNA (messenger RNA) - carries genetic information from nucleus to ribosome - This is made during transcription • tRNA (transfer RNA) - contains an amino acid and an anticodon that binds to a specific mRNA codon • rRNA (ribosomal RNA) - component of ribosomes - made in the nucleolus • microRNA - gene regulatory and defense functions - Amino acids are linked together by peptide bonds. • DNA replication: DNA —> DNA • Transcription: DNA —> RNA Translation: RNA —> proteins • - Codon - 3-nucleotide portion of mRNA that codes for a specific amino acid * Important for the test: translation occurs by reading 5’ to 3’ *AUG is the “start” codon Good luck studying! If you have any questions, feel free to email me at or 22


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